1920] Cranifton — Genitalia of Male Hymetioptera and Other Insects 37 



"s" of Fig. 12), there is some reason to suppose that styliforjm 

 appendages borne on the tenth abdominal segment of certain 

 Trichopteron larvae (see Plate III, fig. 6, "s") may take part in 

 the formation of portions of the genitalia of the adult male, 

 although this matter is greatly in need of further investigation. 



The tenth tergite labeled "ep" in Fig. 11, overlaps the para- 

 procts "pr" which are situated on either side of the anal opening, 

 and bear the cerci "ca." The paraprocts "pr" are latero-ventral 

 structures of the eleventh segment, and are usually interpreted as 

 representing the divided sternite of this segment, although it is 

 quite possible that they represent the protopodite of the uropod 

 whose endopodite forms the cercus. The eleventh tergite of the 

 ephemerid shown in Fig. 11 bears a terminal filament or telofilum 

 "tf." The eleventh tergite is usually atrophied in the higher 

 forms, while the paraprocts "pr" usually unite with the tenth 

 tergite "ep" to form a structure through which the anus opens 

 (i. e. the "proctiger" of higher insects). 



In the blattids (whose parts are of the type serving as the 

 "starting point" for the modifications developing in the various 

 orthopteroid insects) the styli-bearing plates "p" of Fig. 12, are 

 usually indistinguishably united with the ninth sternite "ha," 

 although in the roach shown in Fig. 12, traces of these plates are 

 still retained. The styli, "s," however, usually remain distinct 

 even after the plates bearing them have become indistinguishable 

 fused with the ninth sternite. The penis valves "pv" of Fig. 12, 

 possibly represent the paired organ "pv" of the ephemerid shown 

 in Fig. 11, although the parts are asymmetrically developed in the 

 roach. The tenth tergite "ep" is distinct in most blattids, as is 

 also true of the paraprocts "pr" (Fig. 12); but the eleventh tergite 

 is atrophied in these insects and their immediate relatives. 



A different path of specialization is apparently followed in the 

 higher insects although the condition occurring in these forms is 

 probably a modification of the basic plan exhibited by the Ephem- 

 erida (Fig. 11). Thus in the Prohymenopteron (sawfly) shown in 

 Fig. 17, the tergite of the ninth segment "9*" becomes very small, 

 while the sternite of the ninth segment is very large, and projects 

 beneath the genitalia of the male to form the so-called hypandrium 

 "ha." The tenth tergite "ep" is very small, and the paraprocts 

 "pr" of Fig. 11, which bear the cerci "ca," have united with the 



